Due to the recent vast increase in Internet traffic density, it is urgent to meet the demand of increasing the communication network capacity. One solution to fulfill this demand is the DWDM (Dense Wavelength Division Multiplexing) technique in whose development the U.S.A. and Canada have taken a leading role. As the DWDM technique transmits optical signals of different wavelengths division-multiplexed in a dense form over a single optical fiber, the transmission capacity can be increased by the degree of wavelength division multiplexing. Because of the feature, attention is being focused on the DWDM technique.
Accordingly, it is an object of the present invention to provide a wavelength multiplexing module which is adaptable to DWDM transmission.
A wavelength multiplexing module according to one aspect of the invention comprises:
a plurality of pumping sources for outputting lights of different wavelengths;
a wavelength multiplexer for multiplexing the lights output from the pumping sources, the wavelength multiplexer having optical input sections for respectively receiving the lights output from the pumping sources; and
depolarizers, respectively provided between the optical input sections and the pumping sources,
wherein each of the depolarizer causes a degree of polarization of the light output from an associated one of the pumping sources to approach zero.